The invention relates to an apparatus for the manufacture of cylindrical hollow bodies by means of the shape welding process, this apparatus comprising a connection between a rotatably mounted supporting body which can be driven and a base body onto which the weld material is deposited, this connection, which is effected by means of elastically deformable elements, which are capable of changing in the radial direction.
By the shape welding process, cylindrical hollow bodies are built-up layer by layer, each layer being formed by deposition of molten metal by welding along neighboring tracks which together cover the area of the base body. The weld deposition of the metal may be effected by a welding head, which is moved longitudinally along the body, and if the body is simultaneously axially rotated the metal is deposited along a helical path in forming a layer. A plurality of welding heads may be used so that metal is deposited simultaneously at different positions during the construction of each layer.
It has been found that such weld deposition of metal satisfies high standards, particularly if the layers are generated on the axially rotating body by a powder shielded welding process During the manufacture of cylindrical hollow bodies by the shape welding process shrinkage stresses in the deposited metal occur. There are some proposals to prevent denting or bending of the base body as a result of the shrinkage stresses.
German Pat. No. 3,029,686 discloses an apparatus comprising a connection between a rotatably mounted supporting body and a base body which is capable of changing in the radial direction. This connection is composed of elastically compliant shrinkage elements. The shrinkage elements are designed, in particular, as U-shaped spring elements which possess U-legs parallel to the axis, and which are arranged in the interspace between the supporting body and the base body, spaced from one another at distances which can be selected in both the peripheral and axial directions.
This apparatus enables uniform absorption of the shrinkage stresses to be achieved, these stresses occurring during the manufacture of cylindrical hollow bodies by means of the shape welding process. The elastically compliant shrinkage-elements absorb the shrinkage stresses, but it is not always possible to prevent the supporting body from being subjected to certain deformations. However, changes in the circular shape or diameter variations over the length of the hollow body which is manufactured do not, in general, occur.
In the case of this known apparatus, it is, however, necessary that the elastically compliant shrinkage elements be securely welded both to the supporting body and to the base body. In consequence, the removal of the supporting body from the finished hollow body is possible only by means of a procedure involving damage to the supporting body so that it cannot easily be re-used for the manufacture of further hollow bodies.
A further disadvantage resides in the fact that it is impossible to adapt the apparatus to suit base bodies possessing different internal diameters, so that it is invariably necessary to build a separate apparatus for each diameter. A further cost increase is associated with this problem.
German Pat. No. 2,850,721 discloses an apparatus which can be used repeatedly, and which is also independent of the diameter of the base body employed on any particular occasion. In this apparatus, the radially shiftable connection between the rotatably mounted supporting body, which is driven, and the base body is formed by supporting members which are equipped with a spindle drive in order to enable them to be shifted radially. By this means, it is possible to effect an adjustment to suit different diameters of hollow bodies which have to be produced. However, when using this known apparatus, it is impossible to achieve the absorption of the shrinkage stresses which occur during the shape welding process. When an apparatus of the above-mentioned type is employed, it has been found that the spindle drives have even been destroyed by the shrinkage stresses which occur.